Well bore zone plugging method and apparatus

ABSTRACT

A gamma ray logging tool and a bailer containing a catalyst or curing agent are lowered in a bore hole to a zone therein having a permeability which is to be decreased. A liquid plastic is pumped into the bore hole to the zone, the plastic containing a radioactive tracer detected by the logging tool when the plastic arrives at the zone, whereupon the catalyst is discharged from the bailer and mixed with the liquid plastic, the mixture then being displaced into the zone where it hardens.

United States Patent 1 Glenn, Jr.

[ 1 Jan. 9, 1973- [54] WELL BORE ZONE PLUGGING METHOD AND APPARATUS [75] Inventor: James .1. Glenn, Jr., Long Beach,

Calif.

[73] Assignee: Triangle Service Inc., Long Beach,

Calif.

[22] Filed: Jan. 11, 1971 [21] Appl. No.: 105,481

[52] US. Cl. ..166/253, 166/169, 166/247, 166/295 [51] Int.Cl ..E21b 33/132, E2lb 33/138 [58] Field of Search ..l66/253, 247, 250, 295, 292, 166/286, 294,162,169, 63, 64,113, 65

[56] References Cited UNITED STATES PATENTS 3,250,330 5/1966 Smith, Jr. 166/295 3,176,769 4/1965 Treadway et all. ....l66/295 3,004,599 10/1961 Goodwin et a1. ....l66/292 2,896,716 7/1959 Spurlock ..l66/294 3,261,400 7/1966 Elfrink ..166/292 3,105,549 10/1963 Raulins 166/ 63 X 3,247,900 4/1966 Perry et a1 166/251 3,153,449 10/1964 Lebourg ..l66/286 3,362,477 l/1968 Brandt ..166/295 X 3,379,251 4/1968 Bohn ..l66/286 3,208,525 9/1965 Caldwell et al ..l66/286 X Primary Examiner-Stephen .1 Novosad Attorney-Bernard Kriegel and Kendrick, Subkow & I

Kriegel [57] ABSTRACT 25 Claims, 7 Drawing Figures PATENTEDJAN 9 I975 SHEET 2 [IF 2 Z a u. .T, E 3% v M 2 .1 J 5 WELL BORE ZONE PLUGGING METHOD AND APPARATUS The present invention pertains to reducing the permeability of a zone in a bore hole and more particularly to an apparatus and method for displacing a liquid plastic into the zone which sets up therein to reduce its permeability.

Most well bores include several zones or regions having different permeabilities. During well operation, the rate of flow from each zone to the well bore will, to a large extent, be determined by the relative permeabilities of these different zones. Particularly difficult problems are presented with water entering a producing well and with thief zones taking more water than desired in a water injection well. Reduction of the permeability of zones producing large quantities of water is desirable to decrease the water produced and prevent it from having a detrimental effect on the capacity of the well to produce oil, and also to avoid the cost of disposing of the water. In water injection wells, it is important that the zones be flooded evenly, and that the flood front progresses uniformly toward a producing well. If one zone is taking more than its share of water, the flood cannot recover the maximum amount of oil.

It is known to reduce the permeability of well bore zones by using cement, which is efiective where the plugging action is primarily mechanical or confined to the immediate exposed zone surface. On the other hand, where it is necessary to effect a more substantial sea] and the sealing agent must penetrate the zone, cement has not been found satisfactory because the cement particles filter out and remain on the formation face without penetrating into the zone. The result is the formation of an easily broken or easily by-passed cement layer on the well bore face. Another diff culty with. the use of cement as a plugging material is its setting time. The cement begins to set and harden as soon as it has been mixed with the water, and since the well temperature at the zone to be plugged is usually much greater-than the temperature at the top of the well bore, cement setting is accelerated. Accordingly, it is necessary to allow ample time for placing the cement at the desired zone, with attendant danger of its premature setting in the well bore. In addition, the use of cement is costly because of the expensive equipment required to place it in the well at the desired location.

- It is, therefore, an object of the present invention to provide an improved method and apparatus for decreasing the permeability of one or more well bore zones without using cement.

Another object of the invention is the provision of a method and apparatus for selectively plugging a given region of a well bore with a plastic, which penetrates a substantial distance into the formation surrounding the well bore.

A further object of the invention is the provision of a method and apparatus for plastic plugging a well bore zone, in which the plastic components are mixed at the formation zone to be penetrated.

Yet another object of the invention is to provide a method and apparatus for reducing the permeability of a well bore zone, in which the main body of plastic material and a catalyst or curing agent for effecting its setting are lowered separately into the well bore to the zone, the plastic and catalyst being mixed at the. zone location, such mixture then being forced into the formation zone, thereby precluding premature setting of the plugging material in the well bore.

In the practice of the invention, a quantity of a plastic in a liquid state is disposed at the particular zon'e to be penetrated by-the plastic to reduce the permeability of the zone, the plastic being mixed at the location of the zone with a catalyst, after which the mixture is forced into the zone. Upon setting of the plastic and catalyst mix, the zone is partially or totally blocked.

A suitable plug, such as a sand plug, may be placed in the well bore below the zone or region to be treated preparatory to the introduction of the plastic and catalyst. A bailer carrying a gamma ray detector and containing one of the plastic components, such as the catalyst, for example, is lowered into the well bore and.

located at the region or zone to be treated. A quantity of a liquid having a density substantially the same as the other plastic component is pumped down the bore, followed by a suitable quantity of such other plastic component. A radioactive tracer is included in the other plastic component such that, when it reaches the zone to be treated, the gamma ray detector carried by the bailer will detect its presence and generate a signal transmitted to the top of the well bore indicating that the other plastic or resin has arrived at the desired location. The bailer is then opened and the catalyst ejected therefrom for mixing with the other plastic component.

When bringing the plastic ingredients together along the zone to be treated, the bailer is reciprocated longitudinally several times to insure the thorough mixture of the resin and catalyst. A displacement fluid used to pump the liquid resin down the well bore is then pressurized to force the catalyzed plastic into the formation along the zone where the plastic willharden. After the operation has been completed, any hard plastic or plug that'might remain in the well bore is removed, in a known manner.

This'invention possesses many other advantages and purpose of illustrating the general-principles of the invention; but it is to be understood that such detailed description is not to' be taken in a limiting sense. I

REFERRING TO THE DRAWINGS-2,

FIG. I is a longitudinal section and elevational view of awell bore penetrating a zone to be treated in accordance with the invention, and showing the apparatus of theinvention in the well bore;

FIGS. 2a, 2b and 2c are longitudinal sectional views of the bailer used with the present invention, FIGS. 2b and 2c being lower continuations of FIGS. 2a and 2b, respectively; v v

FIG. 3 is an enlarged longitudinal section of the valve portion of the bailer in open condition;

FIG. 4 is a cross-section taken along the line 4-4 of FIG. 3;

FIG. 5 is a cross-section taken along the line 5-5,of no.3.

As disclosed in FIG. 1, a well bore ltli'ncludes a formation region or zone 11 of relatively high permeability into which a sealant is to be injected for the purpose of reducing its permeability. A casing 12 is located in the well bore, which has a plurality of openings or perforations 13 providing fluid communication between the casing interior and the zone.

A plug (not shown), such as a sand plug, may or may not be placed in the casing 12 below the openings 13, depending upon well conditions and its need. If liquid in the casing cannot be displaced from the region below the perforations, a plug may not be necessary. A tubing string 14 is run in the casing with its lower end disposed above the zone 11 and easing perforations 13, a suitable packer 15 being set in the-well casing to pack-off the annular space between the lower portion of the tubing string and the casing, all in a known manner.

A positive displacement or dump bailer 16 containing a quantity of a liquid plastic catalyst is lowered on a suitable electric cable 17 from the top ofthe well bore,

through the tubing'string to the region-of the zone 11.

As will be more particularly described, the bailer includes displacement or pumping means selectively actuatable to eject the catalyst from the bailer into the well bore. The bailer also carried a gamma ray detector 18, fora purpose to'be described.

To prevent dilution of the polymer or liquid plastic to be pumped down the tubing'string and into the formation, it is preceded by a quantity of a liquid having a density at leastasgreat as that of'the polymer. By way of example, the preceding liquid may comprise a saturated solution of calcium chloride. The liquid plastic, such as a methyl bridge polymer, is pumped into the tubing string on top of the preceding liquid, the quantity of polymer being sufficient to substantially flll the casing along the formation zone to be treated. Since the polymer has a density equal to or less than that of the preceding liquid, it will, in effect, float thereon and remain in a substantially undiluted state while being pumped down the tubingstring and into the casing region surrounded by the formation zone 11. A displacement fluid is pumped into the tubing string on top of the polymer, this displacement fluid, such as brine, being lighter than the polymer so as not to'dilute the latter. The displacement fluid will force the preceding fluid and polymerinto the casing below the tubing string and thereafter, as described below, into the zone to be treated. j I v The polymer includes a radioactive tracer material, for example, the isotope Iodine-131., so that'when the polymer reaches the zone portion of the casing, a signal will be generated by the bailer gamma ray detector 18, indicating that the polymer has arrived at the zone.

An electric command signal initiated at the top of the well bore will effect opening of the bailer and cause the catalyst or curing agent carried within the bailer to be ejected therefrom for mixing with the polymer resin. As is well known in the synthetic resin art, mixture of the catalyst and resin initiates solidification or setting up of the resin. As thecatalyst is being ejected from the bailer into thepolymer mass in the casing, the bailer is moved upwardly to achieve a. relatively uniform distribution of catalyst throughout the entire polymer mass. The'bailer may then be vertically reciprocated to insure a thorough mixing in the well casing of the resin and catalyst. Y

plastic resin used was a methyl bridge polymer termed Cyanoloc 62, manufactured and sold by American Cyanamid, Inc. The catalyst was a saturated solution of sodium bisulfate. Mixture of this particular polymer and catalyst produces a solution which sets up to a fully hardened condition-even at elevated temperatures in approximately 4 minutes. The relative proportions of these materials used were approximately 2.5 gallons of catalyst to 55 gallons of polymer.

Other plastic materials suitable for use in connection with the technique described are available. However, in making a selection of a satisfactory plastic there are certain criteria for acceptability which should be considered. First of all, since the ambient temperature at whichtheplastic is to set up may be an elevated one, the plastic materials must not, have their physical characteristics radically affected by temperature. More particularly, the hardened plastic which sets up in the zone mustbe capable of remaining solid at the temperature existing in the zone. A further selection criterion is that the catalyst resin mixture must not set up too quickly, otherwise there will be insufficient opportunity for displacing it into the zone to effect a proper seal therein. in the example described above, the plastic takes approximately 4 minutes to set upto a. fully hardened condition. This has been found adequate for most pumping operations, even for very deep zones. Of course, plastics exceeding this hardening time can be used, if otherwise acceptable.

When sealing according to the described technique, the most permeable parts" of the zone will take the polymer-catalyst liquid first, and the remaining liquid will then be forced into the next most permeable part of the zone. Accordingly, dependent upon the relative permeability of the different parts of the zone or zones being blocked, anumber of cycles or stages of plastic injection as described many be required to produce a complete sealing of a given zone. -ln this regard, aguide to the progress being made is the magnitude of the pressure required to pump the plastic and catalyst mixinto the zone. That is, the higher the pressure, the lower the permeability of the zone into which the plastic is being forced. A mechanical flowmeter may be used to determine in a more precise manner the injection or production profile.

Since a certain amount of hardened plastic may be left in the casing, it maybe necessary on completion of the operation of injecting the polymer into the zone to clean out the well and remove hardened polymer from the casing, which can be done in a known manner, as through use of a drill bit. v

Reference is made to FIGS. '2 to 5 for the detailed construction of the positive displacement bailer'16. The uppermost end of the bailer includes a generally cylindrical, elongate header 19 having an axial bore 20 extending therethro'ugh. ln the upper end'of the bore 20, there is threadedly received a mechanical and electrical connector 21 interrelating the cable 17 to the 22a and along the tube 27, suitable seal rings carried by the piston, such as O-rings 30 and 31, preventing leakage between the piston and the tube 27 and the cylinder wall 22a. A supply of fluid catalyst 32 fills the container 22 between the lower end of the piston 29 and the upper end of the valve housing 26. To increase the effective weight of the piston, it is secured to an elongate piston weight 29a thereabove surroundingthe tube 27 through the agency of a guide 60 slidable along the tube 27 and piloted within the piston 29 and piston weight 29a,to which it is secured by screws 61.

The lower end of the valve housing or body 26 is threadedly connected to the upper end of a hollow enclosure 33 which contains a reversible electric motor 34 having a rotatable shaft 36 extending through the end closure 62 of the valve housing 26, the lower end of the enclosure 33 including a threaded fitting 37 into which is received a similarly dimensioned fitting of a gamma ray detector 18, which is connected to the cabling 28 through a male connector 38'.

As shown in FIG. 1, affixed to the lowermost end of the bailer 16 beyond the gamma ray detector is a conventional tubing centralizer 39-comprising a plurality of leaf springs 40 yieldably engaging the wall of the well casing 14. These leaf springs are capable of collapsing inwardly to a substantial extent to enable the bailer detector and centralizer to be lowered through the tubing string 14, the springs expanding outwardly into engagement with the casing wall upon movement downwardly from the tubing string, and serving to center the bailer 16 in the wallcasing. As described hereinbelow, the centralizer springs also function as a mechanism for mixing the catalyst ejected fromthe bailer with the polymer pumped down the tubing string into the casing in the region of the perforations 13.

By referring to FIGS. 2b and 3, it-will be noted that the valve housing 26 contains a valve member 41 having a sealing gasket 42 secured to its end bya screw 43. The valve member is shiftable axially in the closure 26,

being prevented from rotating by a screw or key 70 an open condition in which the liquid catalyst 32 can pass through the passage 46 into the valve chamber 47. A plurality of circumferentially spaced orifices 48 are threaded into the wall of the valve body 26 at theupper end of the chamber47 immediately adjacent to the valve seat 45. When the valve member 41 is in its said first and second plugging materials being adapted Y closed position (FIG. 2), the catalyst 32 cannot flow from the chamber 22 to the exterior of the bailer; whereas, when the valve member 41 is in its open condition, the catalyst is capable of flowing from the container 22 through the orifices and into the well casing.

With the valve member 41' closing the passages 46, the bailer is filled with the liquid catalyst through a fill port 80 in the valve body, communicating with a passage 81 opening into the lower end of the container 22. Introduction of the catalyst through the fill port 80 drives the piston 29 and piston weight 294' to an upper position in the container, whereupon a needle valve 82 threaded in the valve body 26 is rotated to close the passage 81.

In operation, during lowering and initial positioning of the bailer at the zone 11, the valve member 41 is maintained in the closed position disclosed in FIG. 2b. When the polymer pumped down the tubing string has arrived at the gamma ray detector 18, a signal is generated in the gamma ray detector by the radioactive iodine, which is transmitted along the cabling 28 to the top of the well bore, indicating to the operator that the polymer has arrived at the bailer location. A command signal from the surface is then transmitted via the cabling 28 to the motor 34, effecting rotation of its shaft 36 in the proper direction," shifting the Y valve member 41 to its open position (FIG. 3), because of the rotation of the threaded shaft portion 36a within the threaded socket 44 of the non-rotatable valve member 41. The weighted drive piston-combination 29, 29a now moves by gravity downwardly in the container 22, forcing the catalyst ahead of it through the passage 46, chamber 47 and orifices 48 out of the'bailer for mixing with the polymer. When the piston 29 reaches its lowermost position '(FIG. 3), and, therefore, has pumped substantially all of the catalyst from the bailer, a command signal transmitted to the motor 34 effects its rotation in a reverse direction to produce upward movement of the valve member 41 to its closed position in engagement'with the valve seat 45.

. As stated above, while the catalyst is being ejected from-thebailer 16, the latter and the centralizer 39 attached thereto are moved upwardly through the surrounding polymer to achieve generally uniform catalyst disposition throughout the entire quantity of polymer', after which the bailer and centralizer '39 are reciprocated to' enhance mixing between the polymer and catalyst. Pressure is then applied to the fluid in the tubing string 17 to force the catalyzed polymerinto the formation zone 1 l, where it sets up andhardens.

'Iclaim: Y

1 A method of plugging a region in a bore hole, cornprising lowering a first fluent plugging material in the hole to said region therein, then lowering'a second fluent plugging material in the bore hole to said region,

- to react with one another and set up to .a hard state,

mixing said first andsecondmaterials in said region and within the bore hole, and displacing the mixture of first and secondmaterials from the bore hole into the formation surrounding the bore hole while said mixture is in a fluent state.

2 ,A method as defined in claim 1; said'first plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst.

3. A method of plugging a region in a bore hole, comprising lowering a first fluent plugging material in the bore hole to said region therein, then lowering a second fluent plugging material in the bore hole to said region, said first and second plugging materials being adapted to react with one another and set up to a hard state, mixing said first and second materials in said region, and displacingthe mixture of first and second materials into .the formation surrounding the bore hole while said mixture is in a fluent state; detecting the arrival of said second material at said region prior to the mixing of said first and second materials.

4. A method of plugging a region in a bore hole, comprising lowering a first fluent plugging material together with a detector in the bore hole to said region therein, then lowering a second fluent plugging material in the bore hole to said region, said second plugging material including a material capable of activating said detector, whereby arrival of said second plugging material at said region generates a signal in said detector transmitted to the top of the bore hole, said first and second plugging materials being adapted to react-with one another and set up to a hard state, mixing said first and second materials in, said region, whereby said mixed materials will harden.

5. A method of plugging a region in a bore hole, comprising lowering a first fluent plugging material together with a detector in the bore hole to said region therein, then lowering a second fluent plugging material in the bore holeto said region, said second plugging material including a material capable of activating said detector, whereby arrival of said second plugging material at said region generates a signal in said detector transmitted to the top of the bore hole, said first and second plugging materials being adapted to react with one another and setup to a hard state, mixing said first and second materials in said region, whereby said mixed materials will harden, and displacing themixtu're of first and second materials into the formation surrounding the bore hole while said mixture is in a fluent state. I 1

6. A method'of plugging a'r'egion in a bore hole, comprising lowering a first, fluent plugging material in the bore hole to said region therein,then lowering a second fluent plugging material in the bore hole to said region, said firstand second-pluggingmaterials being adapted to' react with one another and set up to a hard state, mixing said first andsecond materials-in said region, and displacing the mixture of firstand second materials into the formation'surrounding the bore hole while said mixture is in a fluent state; said first plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst, lowering a detector with said catalyst to said region, said second plugging material including a radioactive material detectable by said detector to generatea signal therein transmitted to the top of the bore hole. 7

7. A method of plugging a region in a bore hole, comprising lowering a bailer containing a first fluent plugging material "in the bore .-hole' to said region 8. A method as defined in claim 7; and displacing the I mixture of first and second materials into the formation surrounding the bore hole while said mixture is in a fluent state.

9. A method as defined in claim 7; said plugging material being a catalyst said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst.

10. A method as defined in claim 7; said first plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst, lowering a detector to said region with said bailer, said second plugging material including a radioactive material detectable by said detector to generate a signal therein transmitted to the top of the bore hole.

11. A method as defined in claim 7; said first plugging material being a catalyst, said second plugging I material comprising a synthetic resin adapted to be catalyzed by said catalyst, lowering'a detector to said region with said bailer, said second plugging material including a radioactive material detectable by said detector to generate a signal therein transmitted to the top of the bore hole, and displacingthe mixture of resin and catalyst into the formation surroundingthe bore hole while said mixture is in a fluent state. 12. A method of plugging aregion in a bore hole containing a tubing string extending to said region, comprising lowering a bailer containing a first fluent plugging material through the-tubing string to said re,- gion, then pumping a second fluent plugging material through the tubing string to said region, said first and second plugging materials being adapted toreact with one another and set up to a hard state, releasing said first material from said bailer after arrival of said second material at said region, and mixing said first and second materials in said region, whereby said mixed materials will harden. l3.'A method as defined in claim 12; introducing a displacingfluid into said tubing string on top of said secondmaterial, and pumping said displacing fluid down said tubing string to displace said mixture of first and second materials in a fluent state into the formation surrounding the bore hole. I

14. A method as defined in claim 12; introducing'a preceding fluid into the tubing string in advance-ofsaid plugging material'to prevent dilution of said "second plugging material.

15. A method as defined in'claim v12; introducing a preceding fluid into the tubing string in advance of said plugging material to prevent dilution "of said second and pumping saidbrine down said'tubin'g string to displace said mixture of first and second-materials in a fluent state into the formation surrounding the bore hole.

17. A method as defined in claim 12; lowering a detector with said bailer through said tubing string, said first plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst and including a radioactive material detectable by said detector to generate a signal therein transmitted to the top of the bore hole.

18. A method as defined in claim 12; lowering a detector with said bailer through said tubing string, said first plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst and including a radioactive material detectable by said detector to generate a signal therein transmitted to the top of the bore hole, introducing a preceding fluid into the tubing string in advance of said synthetic resin to prevent dilution of said synthetic resin, introducing a displacing fluid into said tubing string on top of said synthetic resin, and pumping said displacing fluid down said tubing string to displace said mixture of catalyst and synthetic resin in a fluent state into the formation surrounding the bore hole.

19. A method as defined in claim 12; lowering a de tector with said bailer through said tubing string, said first plugging'material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst and including a radioactive material detectable by said detector to generate a signal thereintransmitted to the top of the bore hole, introducing a solution of calcium chloride into the tubing string in advance of said synthetic resin to prevent dilution of said synthetic resin, introducing brine into said tubing string on top of said'synthetic resin, and pumping said brine down said tubing string to displace said mixture of catalyst and synthetic resin in a fluent state into the formation surrounding the bore hole.,

20. Apparatus for plugging a region in a bore hole containing a tubing stringextendihg to, said region, comprising an initially closed bailer adapted to contain a first fluent plugging material and capable of being lowered through the tubing string to said region, a detector lowered with the bailer to said region and responsive to a second fluent plugging material pumped down the tubing string for detecting the arrival at said regionof said second fluid material, said bailer including means for opening said bailer for the discharge therefrom of said first plugging material into said second plugging material after arrival of said second plugging material at said region. v

21. Apparatus for plugging a region in a bore hole including a radioactivetracer, said detector comprising means responsive to said tracer for producing an information signal. I

22. Apparatus for plugging a region in a bore hole containing a tubing string extending to said region, comprising an initially closed bailer adapted to contain a first fluent plugging material and capable of being lowered through the tubing string to said region, a detector lowered with'the bailer to said region for detecting the arrival at said region of a second fluent plugging material pumped down the tubing string, said bailer including means for opening said'bailer for the discharge therefrom of said first plugging materialinto said 'second plugging material after arrival of said second plugging material 'at said region; saidsecond material including a radioactive iodine, said detector comprising gamma ray detection means responsive to the presence of said iodine for producing an information signal.

23. Apparatus for plugging a region in a bore hole containing a tubing'string extending to said.- region,

comprising an initially closed bailer adapted to contain a first fluent'plugging material and capable of being lowered through the tubing string to said region, a'detector lowered with the bailer to said region for detect ing the arrival-at said region of a second fluent plugging material pumped down the tubing string, said bailer including'means for opening said bailer for the discharge therefrom of said first plugging material into said second plugging material after arrival of said second plugging material at said region; and mixing means secured .to said bailer for mixing said materials in response to longitudinal movement of said bailer-and mixing means in the bore hole.

24.- Apparatus asdefined in claim 23; said mixing means comprising a centralizer adapted to center the bailer in the bore hole.

' 25. Apparatus as defined in claim 23; said mixing means comprising ;a centralizer adapted to center the bailer'in the bore hole, said second material including radioactive iodine, said detector comprising gamma ray detection means responsive to the presence of sai iodine/for producing'an information signal. I I

i i i t i 

2. A method as defined in claim 1; said first plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst.
 3. A method of plugging a region in a bore hole, comprising lowering a first fluent plugging material in the bore hole to said region therein, then lowering a second fluent plugging material in the bore hole to said region, said first and second plugging materials being adapted to react with one another and set up to a hard state, mixing said first and second materials in said region, and displacing the mixture of first and second materials into the formation surrounding the bore hole while said mixture is in a fluent state; detecting the arrival of said second material at said region prior to the mixing of said first and second materials.
 4. A method of plugging a region in a bore hole, comprising lowering a first fluent plugging material together with a detector in the bore hole to said region therein, then lowering a second fluent plugging material in the bore hole to said region, said second plugging material including a material capable of activating said detector, whereby arrival of said second plugging material at said region generates a signal in said detector transmitted to the top of the bore hole, said first and second plugging materials being adapted to react with one another and set up to a hard state, mixing said first and second materials in said region, whereby said mixed materials will harden.
 5. A method of plugging a region in a bore hole, comprising lowering a first fluent plugging material together with a detector in the bore hole to said region therein, then lowering a second fluent plugging material in the bore hole to said region, said second plugging material including a material capable of activating said detector, whereby arrival of said second plugging material at said region generates a signal in said detector transmitted to the top of the bore hole, said first and second plugging materials being adapted to react with one another and set up to a hard state, mixing said first and second materials in said region, whereby said mixed materials will harden, and displacing the mixture of first and second materials into the formation surrounding the bore hole while said mixtUre is in a fluent state.
 6. A method of plugging a region in a bore hole, comprising lowering a first fluent plugging material in the bore hole to said region therein, then lowering a second fluent plugging material in the bore hole to said region, said first and second plugging materials being adapted to react with one another and set up to a hard state, mixing said first and second materials in said region, and displacing the mixture of first and second materials into the formation surrounding the bore hole while said mixture is in a fluent state; said first plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst, lowering a detector with said catalyst to said region, said second plugging material including a radioactive material detectable by said detector to generate a signal therein transmitted to the top of the bore hole.
 7. A method of plugging a region in a bore hole, comprising lowering a bailer containing a first fluent plugging material in the bore hole to said region therein, then lowering a second fluent plugging material in the bore hole to said region, said first and second materials being adapted to react with one another and set up to a hard state, releasing said first material from said bailer after arrival of said second material at said region, and mixing said first and second materials in said region, whereby said mixed materials will harden.
 8. A method as defined in claim 7; and displacing the mixture of first and second materials into the formation surrounding the bore hole while said mixture is in a fluent state.
 9. A method as defined in claim 7; said plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst.
 10. A method as defined in claim 7; said first plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst, lowering a detector to said region with said bailer, said second plugging material including a radioactive material detectable by said detector to generate a signal therein transmitted to the top of the bore hole.
 11. A method as defined in claim 7; said first plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst, lowering a detector to said region with said bailer, said second plugging material including a radioactive material detectable by said detector to generate a signal therein transmitted to the top of the bore hole, and displacing the mixture of resin and catalyst into the formation surrounding the bore hole while said mixture is in a fluent state.
 12. A method of plugging a region in a bore hole containing a tubing string extending to said region, comprising lowering a bailer containing a first fluent plugging material through the tubing string to said region, then pumping a second fluent plugging material through the tubing string to said region, said first and second plugging materials being adapted to react with one another and set up to a hard state, releasing said first material from said bailer after arrival of said second material at said region, and mixing said first and second materials in said region, whereby said mixed materials will harden.
 13. A method as defined in claim 12; introducing a displacing fluid into said tubing string on top of said second material, and pumping said displacing fluid down said tubing string to displace said mixture of first and second materials in a fluent state into the formation surrounding the bore hole.
 14. A method as defined in claim 12; introducing a preceding fluid into the tubing string in advance of said plugging material to prevent dilution of said second plugging material.
 15. A method as defined in claim 12; introducing a preceding fluid into the tubing string in advance of said plugging material to prevent dilution of said second plugGing material, introducing a displacing fluid into said tubing string on top of said second material, and pumping said displacing fluid down said tubing string to displace said mixture of first and second materials in a fluent state into the formation surrounding the bore hole.
 16. A method as defined in claim 12; introducing a solution of calcium chloride into the tubing string in advance of said second plugging material to prevent dilution of said second plugging material, introducing brine into said tubing string on top of said second material, and pumping said brine down said tubing string to displace said mixture of first and second materials in a fluent state into the formation surrounding the bore hole.
 17. A method as defined in claim 12; lowering a detector with said bailer through said tubing string, said first plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst and including a radioactive material detectable by said detector to generate a signal therein transmitted to the top of the bore hole.
 18. A method as defined in claim 12; lowering a detector with said bailer through said tubing string, said first plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst and including a radioactive material detectable by said detector to generate a signal therein transmitted to the top of the bore hole, introducing a preceding fluid into the tubing string in advance of said synthetic resin to prevent dilution of said synthetic resin, introducing a displacing fluid into said tubing string on top of said synthetic resin, and pumping said displacing fluid down said tubing string to displace said mixture of catalyst and synthetic resin in a fluent state into the formation surrounding the bore hole.
 19. A method as defined in claim 12; lowering a detector with said bailer through said tubing string, said first plugging material being a catalyst, said second plugging material comprising a synthetic resin adapted to be catalyzed by said catalyst and including a radioactive material detectable by said detector to generate a signal therein transmitted to the top of the bore hole, introducing a solution of calcium chloride into the tubing string in advance of said synthetic resin to prevent dilution of said synthetic resin, introducing brine into said tubing string on top of said synthetic resin, and pumping said brine down said tubing string to displace said mixture of catalyst and synthetic resin in a fluent state into the formation surrounding the bore hole.
 20. Apparatus for plugging a region in a bore hole containing a tubing string extending to said region, comprising an initially closed bailer adapted to contain a first fluent plugging material and capable of being lowered through the tubing string to said region, a detector lowered with the bailer to said region and responsive to a second fluent plugging material pumped down the tubing string for detecting the arrival at said region of said second fluid material, said bailer including means for opening said bailer for the discharge therefrom of said first plugging material into said second plugging material after arrival of said second plugging material at said region.
 21. Apparatus for plugging a region in a bore hole containing a tubing string extending to said region, comprising an initially closed bailer adapted to contain a first fluent plugging material and capable of being lowered through the tubing string to said region, a detector lowered with the bailer to said region for detecting the arrival at said region of a second fluent plugging material pumped down the tubing string, said bailer including means for opening said bailer for the discharge therefrom of said first plugging material into said second plugging material after arrival of said second plugging material at said region; said second material including a radioactive tracer, said detector comprising means responsive to said tracer for producing an information signal.
 22. Apparatus for plugging a region in a bore hole containing a tubing string extending to said region, comprising an initially closed bailer adapted to contain a first fluent plugging material and capable of being lowered through the tubing string to said region, a detector lowered with the bailer to said region for detecting the arrival at said region of a second fluent plugging material pumped down the tubing string, said bailer including means for opening said bailer for the discharge therefrom of said first plugging material into said second plugging material after arrival of said second plugging material at said region; said second material including a radioactive iodine, said detector comprising gamma ray detection means responsive to the presence of said iodine for producing an information signal.
 23. Apparatus for plugging a region in a bore hole containing a tubing string extending to said region, comprising an initially closed bailer adapted to contain a first fluent plugging material and capable of being lowered through the tubing string to said region, a detector lowered with the bailer to said region for detecting the arrival at said region of a second fluent plugging material pumped down the tubing string, said bailer including means for opening said bailer for the discharge therefrom of said first plugging material into said second plugging material after arrival of said second plugging material at said region; and mixing means secured to said bailer for mixing said materials in response to longitudinal movement of said bailer and mixing means in the bore hole.
 24. Apparatus as defined in claim 23; said mixing means comprising a centralizer adapted to center the bailer in the bore hole.
 25. Apparatus as defined in claim 23; said mixing means comprising a centralizer adapted to center the bailer in the bore hole, said second material including radioactive iodine, said detector comprising gamma ray detection means responsive to the presence of said iodine for producing an information signal. 